The present invention relates to a polychromatic monolithic semiconductor assembly comprising several electroluminescent diodes emitting in different wavelength ranges and formed by a substrate on which at least two epitaxial layers are superimposed.
The present invention also relates to a method of manufacturing said monolithic semiconductor device.
Electroluminescent diodes are used for visual display purposes, notably in the techniques of data processing. A binary logic state may be displayed by means of an electroluminescent diode having two states: illuminated indicator, extinguished indicator. However, in the case of strong ambient light, the reflection effects upon the optics of the indicator may entail interpretation errors. For that reason it is to be preferred to display the various logic states by means of indicators having several colours, for example, a red indicator and a green indicator. A first possibility consists in placing the required indicators besides each other, each having its own envelope and optics. The space required by such an arrangement rapidly becomes prohibitive.
In order to avoid this drawback it has been tried to manufacture devices comprising two superimposed indicators, one emitting red, the other emitting green, while using for one of them a material which is transparent to the light emitted by the other.
Such a device is described notably in French Patent Specification 2,069,256. However, the transparency of the regions emitting green light is not perfect. In addition, the manufacture of the structure requires a large number of delicate operations to obtain materials of alternate conductivity types susceptible to forming junctions presenting a good radiation efficiency as well as an adequate transparency. Moreover these devices necessitate local etching operations for making contacts on different planes, which operations present risks and numerous difficulties.